So my dad used to be a drug addict and got caught about 2 years ago. Sat in jail for 9 months. Got and was clean. Well we haven't had a great relationship since. Anyways he's sent me long messages in the past telling me I can't judge him for the man he used to be. And I need to forgive him. So I came to my senses and did. Well the other day he left this leather bag at home. And me and my mom has been suspicious because he's been acting like he used to. So she opened it and pulled out 2 baggies and a straw .. I'm beyond pissed. She wasn't going to say anything. And we plan on leaving soon. But they got into an argument the other night and she told him we seen it. Well she said for hours he tried to convince her she  didn't see what what she had seen. And that she was crazy. So she told him I seen it too. And she told me today he was gonna probably talk to me. And to not give in to him. To tell him I know what I seen. And earlier he told me that he needed to talk to me tonight. What should I say ?